Magnetic Field Imaging (SQUID and more) - eufanet

SQUID at Package-Level (C4 bump)IRCurrent: 125 µADistance: 450 µmIRCurrent: 8.8 µADistance: 450 µm5

SQUID at Die-Level (back-side)6

SQUID at Die-Level (front-side)OpticalCurrent DensityOverlay2.5 mm7

GMR at Die-Level (front-side)OpticalCurrent DensityOverlay8

GMR at Die-Level (wafer part using probes)Optical ImageCurrent Image30 µm100 µm0.3 µm lines with0.3 µm spacingI = 500 µA9

Performance of Magnetic Sensors10 10000 mACurrent11000mA100 100 µA10 µA 101 µA1GMRFibre/SQUID potentialSQUIDsample in vacuum100 0.1 nAFront Side Back Side Packaging0.1 1 10 100 1000Separation Distance (µm)S/N = 10; TC = 3 ms10

Comparison between sensors• SQUID– Most sensitive– Ideal for large working distances ≥ 100 µm– Localize defects to 3 µm• Magnetoresitive (GMR)– Less sensitive than SQUID– Good for short working distances of a few microns– Sub-micron resolution when very close• Fibre/SQUID– Less sensitive than SQUID, but can be better than GMR– Good for short working distances of a few microns– Natural high aspect ratio of tip is good for working in cavities– Sub-micron resolution when very close11

Implementation Model• Coarse scan with SQUID toisolate component• If defect is in the die, thenthin the die and fine scanwith SQUID• Locally open a cavity (laser;FIB)• Scan with magnetoresistivesensor or fibre/SQUID.12